Research On Test System-Oriented Virtual Instrument Design And Its Application

A virtual instrument consists of an industry-standard computer or workstation equipped with powerful application software, modularization hardware such as plug-in boards, and driver software, which together perform the functions of traditional instruments. Through deeply studying the state of the art of virtual instrument at home and abroad, a virtual-instrument application model of test system-oriented design was designed and proposed in this paper for the existing problems found in the process of developing virtual instrument and the developing request of the conners in the mechanical engineering test field. Furthermore, the pile test system, strain test system and virtual test laboratory were designed and developed respectively by applying their own design model. The main work is listed as follows.First, an application model of test system-oriented design including state-machine model for single instrument development and notification-instrument-queue model for test system development was designed and proposed by introducing the related design principle of software engineering into the application design of virtual instrument.Second, the use case and activity diagrams of pile test system based on low-strain instant mechanical impedance method were protracted in Rational Rose through learning about the fundamental theory and applying the instant mechanical impedance method to test the integrity and bearing capacity of pile foundation. At the same time, each application software was wrote in LabVIEW applying its own state-machine model.Third, the use case and activity diagrams of strain test system were protracted in Rational Rose. A stain test application was developed in LabVIEW according to its own state-machine model, which is capable of managing and controlling the input module of SCXI-1520 universal strain gauge effectively. The conventional strain test can be done by applying this strain test system.Fourth, the use case diagram of virtual test laboratory was protracted in Rational Rose. According to the use case diagram, a virtual test laboratory comes into being.The instruments included in the virtual test laboratory were developed in LabVIEW by applying their own state-machine models in test system-oriented design, and the test systems were realized in LabVIEW by applying the notification-instrument-queue model in test system-oriented design. Finally, the pile test analyzer and B&K2034 analyzer were used to acquire and analyze the normal signal of the integral pile outputed from the cassette data recorder respectively. Via comparing their both test results, it is found that the virtual pile test analyzer can be competent to test the integrity and bearing capacity of pile foundation with credible test performance, plentiful analysis function and high efficiency on the spot. Meanwhile, the software test was carried out respectively from the program's practice request, program's implementation performance, program's memory usage and program structure to the strain test instrument and the virtual test laboratory. The applications were further improved.